1. Field of the Invention
The present invention relates to a hybrid type working machine which converts kinetic energy or potential energy into electric energy, accumulates electricity in a charge accumulating device, and drives a driving system by using accumulated electric energy.
Priority is claimed on Japanese Patent Application No. 2009-052197 filed Mar. 5, 2009 and Japanese Patent Application No. 2009-262062 filed Nov. 17, 2009, the content of which is incorporated herein by reference.
2. Description of the Related Art
In recent years, out of consideration for the environment, improvements in performance, such as fuel savings, lower pollution, and lower noise, have been demanded in power generating machines, such as construction working machines. In order to meet the demand, working machines such as hydraulic shovels using an electric motor instead of or to assist a hydraulic pump have been introduced. In a working machine attached with the electric motor, excessive kinetic energy generated from the electric motor is converted into electric energy, and accumulated in a capacitor or the like. As the capacitor, for example, an electric double-layer condenser (capacitor) is used.
The capacitor deteriorates over long-term usage due to repeating charge/discharge operations, overcharging, overdischarging, or heating. The deterioration state may be determined by measuring the internal resistance of the capacitor (refer to JP-A-2007-155586).